In recent years much attention has been given to the design and construction of impact attenuators or barriers to control the rate of deceleration of an errant vehicle as it approaches an obstruction or a fixed hazard adjacent a highway. Examples of such impact attenuators which have been used successfully are disclosed in U.S. Pat. Nos. 3,606,258 and 3,674,115. Other prior proposals are reflected in U.S. Pat. Nos. 3,643,924, 3,856,268 and 3,880,404.
In general each of these devices is of substantial mass and effects deceleration of the impacting vehicle by momentum exchange. In some cases, for example, the barrier disclosed in U.S. Pat. No. 3,606,258 the unit is sacrificial and is intended to be partially or totally destroyed upon impact. In other cases, such as disclosed in U.S. Pat. No. 3,674,115, the barrier is intended to be reusable. However, barriers of this type are relatively costly and frequently require substantial repair or service before they may be reused.
Other impact attenuators employ steel drums or bands which, upon impact, are permanently deformed and which accordingly can not be reused. An example of this type of barrier is disclosed in U.S. Pat. No. 3,141,655.
Neither these prior proposals nor any other presently known prior proposal satisfies the specialized and rigorous requirements imposed by a truck mounted impact attenuator.